Liquid crystal displays are commonly used as display devices for compact electronic apparatuses, because they not only provide good quality images with little power but also are very thin. The liquid crystals in a liquid crystal display do not emit any light themselves. The liquid crystals have to be lit by a light source so as to clearly and sharply display text and images. Thus, a backlight module for an LCD is generally needed.
FIG. 9 is a schematic, exploded view of a conventional backlight module. The backlight module 1 includes two prism films 16, a diffusing film 15, a light guide plate 14, a plastic frame 17, a reflective film 13, and a bottom tray 18 arranged top to bottom in that order. The light guide plate 14 includes a light incident surface 141, and a light emitting surface 142 adjoining the light incident surface 141. The diffusing film 15 and the prism films 16 are disposed adjacent to the light emitting surface 142 of the light guide plate 14. The backlight module 1 further includes a flexible printed circuit (FPC) 12, and three light emitting diodes (LED) 11 connected with the FPC 12. The FPC 12 provides power for the LEDs 11. The LEDs 11 are disposed adjacent to the light incident surface 141 of the light guide plate 14. Light beams emitted by the LEDs 11 enter the light guide plate 14 through the light incident surface 141, and then are emitted from the light emitting surface 142.
The FPC 12 is arranged adjacent to the light incident surface 141 of the light guide plate 14, and the diffusing film 15 and the prism films 16 are arranged on the light emitting surface 142 of the light guide plate 14. It is difficult to obtain an exact fit when assembling the FPC 12, the diffusing film 15, and the prism films 16 together. Further, even if a compact assembly is attained, the assembly may loosen and become unstable when the backlight module 1 is used.
What is needed, therefore, is a backlight module in which the FPC and optical films thereof are compactly and stably assembled together, preferably without any gaps therebetween.